Many polymer-based articles are manufactured by injection, additive manufacturing, biaxial drawing, pipe extrusion, and other molding processes. In order to obtain good mechanical properties, different approaches have been attempted, such as use of fillers to reinforce the polymers. Despite advances in the art and the success of many filled polymer compositions, there remains a continuing need for improved combinations of properties such as higher modulus, improved ductility, improved impact, and/or improved melt flow characteristics, so that molding operations can be performed more rapidly and with improved economics. Typically, it is difficult to obtain good complex viscosity, extensional viscosity, tensile modulus, and impact strength in a particular polymer composition.
Polytetrafluoroethylene (PTFE) fibers have been used as fillers in polymer compositions, but can aggregate in the matrix resin, making it very difficult to obtain a uniform composition. Polytetrafluoroethylene and other fluoropolymers have also been used as additives in thermoplastic polymers in order to improve certain properties of the polymers. The use of relatively small amounts, for example about 0.1 to about 1 percent by weight, of fluoropolymers as an anti-drip additive in flame retardant grades of thermoplastic resin molding compositions is described, for example, in U.S. Pat. Nos. 4,810,739, 4,579,906, and 4,810,739. The use of sintered PTFE in highly filled thermoplastic compositions as low friction additives is disclosed in U.S. Pat. No. 5,879,791. A drawback to the use of fluoropolymer additives exists, however, in that such additives have poor dispersibility in many polymers.
Therefore, there is a continuing in the art for compositions, methods, and articles that can provide balanced mechanical and rheological property profiles.